There are many mathematical models for the position sensorless control of permanent magnet synchronous motors (PMSMs), and various position sensorless control methods have already proposed. However, it is necessary to select a control model according to the objective from characteristics of the EMF phase and the robustness against to the motor parameters. An Imaginary Electromotive Force (IEMF) expression can clarify the differences of these models. This paper discusses the characteristics of each model including the Extended Electromotive Force model for position sensorless control that can be applied to the standstill / low speed range from the middle / high speed range. Finally, we show that this IEMF expression is extremely useful in discussing and designing characteristics of the control models of PMSMs.
This paper proposes an optimal coil layout of wireless power transfer (WPT) systems for underwater vehicles (UVs). The power supply station adopts a multi-coil arrangement with a double layer, and the UV also uses two receiving coils. The proposed WPT system for UVs has a reasonable advantage, where it does not request to adjust the relative position of coils. This paper experimentally discusses an optimal coil layout based on measurement results of a coupling coefficient. As a result, the proposed coil arrangement with the geometry rule realizes a certain power transfer under any positions and directions of UVs.
Image registration plays a very important role in a camera-based remote sensing system. This paper discusses a 2D fast Fourier transform (FFT)-based method, which is well known for its easy implementation, accuracy, and robustness. The problem with the FFT-based method is that its robustness and accuracy highly depend on some preprocessing such as the design of a bandpass filter and subpixel estimation. This paper provided solutions for its algorithm design and tuning issues. Finally, the evaluation based on the image dataset and the actual images demonstrated its effectiveness.
This paper proposes a method to design the control system of a traction inverter for the purpose of an increase in regenerative brake power. In a DC-electrified railway system, it is possible to transmit more regenerative brake power to an accelerating train by maintaining a higher DC input voltage of the regenerating train. On the other hand, regenerative brake control of a traction motor according to the DC input voltage of a traction inverter is generally applied. With regard to the proportional gain of this control system, the higher gain contributes to an increase in the DC input voltage in regeneration. However, there is a possibility that the control system can become unstable by applying higher gain. Considering the trade-off between the energy saving effect and the stability, this paper proposes a method to design the maximum gain that keeps the traction circuit stable. At first, a linearized model for the proposed method which includes the model of the traction system, its control system and DC feeder circuit is introduced. Further, this paper reveals that the proposed method keeps the control system stable by using real scaled experiments.
This paper proposes a novel dual active bridge (DAB) converter that has an auxiliary inductor and a bi-directional switch connected in parallel to a transformer to achieve zero voltage switching (ZVS) and reduce the inductor current over a wide load range and wide battery voltage variation. In the proposed converter, the equivalent magnetizing inductance is changed by switching the auxiliary inductance depending on the output power. To achieve ZVS at a light load, the equivalent magnetizing current is increased by connecting the auxiliary inductance in parallel. In addition, the inductor current of the low voltage (LV) side is also reduced irrespective of a leakage inductance of a high frequency transformer. At a heavy load, the equivalent magnetizing current is reduced without connecting the auxiliary inductance because ZVS is achieved without any increment of the equivalent magnetizing current. In addition, the auxiliary inductance is switched without the occurrence of DC-offset of the auxiliary-inductor current and the surge voltage of a bi-directional switch. In the experimental results, the ZVS range is extended by up to 49%. In addition, the converter loss at a light load is reduced by up to 36.1%. A high efficiency in the wide load is achieved by the switched auxiliary inductance.
A photovoltaic (PV) system with batteries (BTs) is expected to be an effective system for coping with the energy issues that we will face in the future. This paper establishes an energy system with PVs and batteries in order to improve the utilization rate of the power supplied from PVs and batteries to on-premise loads. An external transducer is used to measure the power received from the utility grid. Depending on the measured receiving power, constant receiving power control and power factor control functions for power conditioning systems (PCSs) are utilized to improve the power utilization ratio. The effectiveness of this system will be verified using actual equipment.
In railway lines where trains are running densely, a small increase in dwell time causes a delay and the delay tends to expand and propagate to many other trains. One method to avoid such delays is to increase buffer times between trains. The increase of buffer time, however, may cause an expansion of headway and we may have to decrease the frequency, which is never allowed in a congested railway line. In this paper, we propose a procedure to obtain a timetable in which enough buffer time exists without reducing the frequency of trains. Our key idea is to find a train performance curve that minimizes the departure-arrival interval of trains and make use of the generated time to increase the buffer times. In this process, we do not stick to the idea that travel times of trains have to be minimized. Following this procedure, we can increase the buffer times without reducing the frequency. We have applied our procedure to actual timetables and confirmed that our procedure works well.
A free-piston engine linear generator system is expected to be used as a high-efficiency energy conversion device for a series hybrid electric vehicle. The piston action can be controlled using generation control because this system has no crank mechanism. The copper loss is reduced by using output dispersion between the expansion and compression stroke for a longer stroke. We built a power generation experiment device that simulates combustion and power generation with two motors. By increasing the stroke after the scavenging point, the output power between the expansion stroke and the compression stroke was dispersed, and the copper loss was reduced by 23%.
Partial disconnection of element conductors in AC power cords of household electric appliances or in extension cords is a major cause of fire accidents originating from electric equipment. This kind of disconnection usually occurs in cords that have suffered from mechanical stress. Safety devices based on a reliable method for detecting the disconnection of element conductors have a great potential for preventing accidental fires. In this study, a series of laboratory experiments are carried out using a 100-V AC power cord, where 49 out of 50 element conductors are cut artificially. The temperature of the intact element conductor rises due to Joule heating and is finally disconnected by arc discharge. A fire-prevention device that responds to the anomaly in the voltage waveform observed during arc discharge could be designed.
This paper proposes three new rotor phase estimation methods for sensorless drives of synchronous reluctance motors (SynRMs). The methods can estimate the phase of positive or negative salient poles without errors as a rotor phase by using the generalized flux estimation algorithm. The algorithm was originally developed for estimating the rotor flux of PMSMs with permanent magnet in the rotor. Even though SynRMs do not have rotor flux at all, this paper succeeds in applying the algorithm to phase estimation problem of SynRMs by segmenting the stator reaction flux into “in-phase flux” and “phase-inclusion flux. ” The former does not have rotor phase information, but the latter does. The algorithm is applied to estimating the phase-inclusion flux out of the stator flux. The effectiveness and usefulness of the proposed methods are verified through extensive simulations.
Instabilities due to mutual interactions between inverters and grid impedance are observed sometimes. This paper proposes a new stabilization method, which improves the output frequency impedance characteristics, satisfying the Nyquist stability criterion. The principle is that the output impedance is designed to be passive with the feedfoward loop characteristics and the system is stable even for an unknown grid system impedance. The design principle for the proposed stabilization method is described and investigated and validated on the basis of simulation and experimental results.
The single-phase diode rectifier offers several desirable features such as a simple topology, low high-frequency noise, high reliability, and high environmental durability. However, diode rectifiers produce undesirable lower-order harmonics in the input current. To overcome this problem, the authors propose a single-phase voltage-doubler diode rectifier without active switching devices, which meets to the regulations of IEEE Std. 519-2014. In this paper, the authors validate of the proposed rectifier (2.2kW, 120V/60Hz) through experimental results.